The present invention relates to apparatuses and methods used in medical treatment of a distal radius fracture, and, more particularly, to such apparatuses and methods in which an extension from a volar fixation plate beyond the watershed line is used.
The forearm has two large bones, the radius and the ulna, which run parallel to one another. The proximal end of the radius is at the lateral side of the elbow and extends all the way to the thumb side of the wrist which is the distal end of the radius (from a reference position in which the palm of the hand faces forward). The radius can also be divided in its other dimensions. For example the palm side of the radius bone is called the “volar” and the other side is called “dorsal”. The volar distal radius therefore refers to the palm side of the distal radius. The most prominent region (the part that sticks out like a ridge line) of the volar distal radius is called the “watershed line”. A distal radius fracture is a common bone fracture of the distal end of the radius in the forearm, next to the wrist joint. FIG. 1 shows a “watershed line” 15 across a distal radius.
Surgical implantation of a fixation plate to guide healing of the bone has helped revolutionize treatment of distal radius injuries. The plate is fixed adjacent to the bone to be healed and is held in place using screws. There are many different techniques for treating distal radius fractures including dorsal plating, fragment specific fixation, non-spanning external fixation, volar plating, spanning internal fixation plates.
Locked volar plating is a commonly used technique that has significantly improved the value of treatment by offering a patient with a distal radius fracture early return to work, normal lifestyle, etc. The volar fixation plate is implanted in the body and placed adjacent to but external to the volar side of the radius bone. The volar plate has holes and is affixed by screws that run through holes in the plate. There are two types of screws which are used with these plates, non-locking and locking. Non-locking screws are like traditional screws with a normal appearing head. They only fix to the bone and not to the plate. Locking screws have a smaller diameter head which is threaded. The head of a locking screw locks to the plate within one of the holes in the plate. Locking and non-locking screws typically are placed perpendicular or within a range of approximately 15 degrees from perpendicular to the surface of the plate i.e. they can have a somewhat variable angle within which they can lock to the plate.
Notwithstanding its value, a well known complication of volar plating is irritation and/or rupture of the tendons, especially flexor tendons. The idea is to keep the bone fragments of the fracture together securely without causing irritation or rupture of the tendons. The most common way to position the volar plate is to position it at or just proximal to the watershed line of the distal radius, as shown in FIG. 3 (prior art). This has the advantage that it minimizes the risk of flexor tendon irritation that arises if the plate is distal to the watershed line. An alternative place to position the plate is distal to the watershed line of the distal radius, as shown in FIG. 2 (prior art).
There is a well known concern the art to avoid having volar fixation plates project beyond or above the watershed line. For example, as advocated by a prominent orthopedic surgeon, in Volar Plate Fixation of Distal Radius Fractures by Jorge Orbay, M.D., Hand Clinic 21 (2005) 347-354 at page 348, it states that a “properly designed volar plate must provide sufficient distal buttressing to control the volar marginal fragment but must not project beyond or above the watershed line to prevent contact with flexor tendons.” Since flexor tendons pass directly over the watershed line, they can be chronically irritated by the metal plate and ultimately rupture if the plate is distal to the watershed line. In fact, the Journal of Bone and Joint Surgery reported that a more distally placed plate is associated with a 4% risk of flexor tendon rupture compared to 0% for a more proximally placed plate design. Flexor tendon rupture is a serious and dreaded complication of distal radius fixation, and is occurring with greater frequency since the advent of volar locking plates (although it can also occur as a complication of dorsal plating if a screw protrudes through the volar cortex of the radius).
However, when the distal radius fracture has small bone fragments, for example in the volar/ulnar corner, many orthopedic surgeons feel that a plate proximal to the watershed line will not capture the fragment so it is necessary to put the volar locking plate distal to the watershed line or add additional forms of fixation to support these small but very important bone fragments at the distal part of the fracture, especially at the volar/ulnar corner. The small bone fragments at the ulnar/volar corner are critical for joint stability. The volar/ulnar corner is hard to buttress or secure with a screw. However, Dr. Orbay, the previously mentioned orthopedic surgeon who advocates positioning the volar plate proximal to the watershed line maintains that the preferred position of the volar plate is proximal to the watershed line even in the case of small volar rim bone fragments since he maintains that these small bone fragments can be adequately supported by use of a K-wire technique. However, if K-wires are used in volar plating the wrist must be immobilized until the fracture is adequately healed, which is usually 6 weeks in contrast to the 2 weeks required if rigid fixation with a plate and/or screws is used. K-wires can also be potential passages for bacteria, can break or bend, can lose fixation and can migrate. In addition, for very small but critical bone fragments, the K-wire technique is not entirely effective because it does not provide rigid fixation like a screw does.
There is a compelling need to have a distal radius fixation plate that avoids flexor tendon irritation but which is secure enough to provide fixation for the small but very important bone fragments of the volar/ulnar corner of the radius that are critical for joint stability and to do so without the disadvantages of the prior art.